Insulating film material containing an organic silane compound, its production method and semiconductor device

ABSTRACT

An insulating film material formed by chemical vapor deposition, which contains an organic silane compound having such a structure that at least one secondary hydrocarbon group and/or tertiary hydrocarbon group is directly bonded to a silicon atom.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a low-dielectric constantinterlayer insulating film material used in multilevel interconnectiontechnology in logic ULSI. Particularly, it relates to an insulating filmmaterial containing a silane compound for plasma polymerization, itsproduction method and its use.

[0003] 2. Discussion of Background

[0004] In the production technology in the field of integrated circuitin an electronics industry, demand for high integration and high speedhas been increasing. With respect to silicon ULSI, particularly logicULSI, performance of the wiring which connects MOSFET, rather than theperformance of MOSFET itself by its miniaturization has beenproblematic. Namely, in order to overcome the problem of wiring delaydue to multilevel interconnection, reduction of wiring resistance andreduction of capacity between wirings and between layers have beenrequired.

[0005] Accordingly, at present, introduction of copper wiring having alow electric resistance and having a migration resistance, instead ofaluminum wiring used for the most part of the integrated circuit, isessential, and a process comprising seed formation by sputtering orchemical vapor deposition (hereinafter referred to simply as CVD)method, followed by copper plating, has been used practically.

[0006] As the low-dielectric constant interlayer insulating filmmaterial, various ones have been proposed. Heretofore, as the inorganicsystem, silicon dioxide (SiO₂), silicon nitride and phosphosilicateglass, and as the organic system, polyimides have been employed. Inrecent years, with a purpose of obtaining a more homogeneous interlayerinsulating film, it has been proposed that a tetraethoxysilane monomeris preliminarily hydrolyzed, i.e., subjected to polycondensation toobtain SiO₂, which is used as a coating material called “spin on glass”(inorganic SOG), and it has been proposed to use a polysiloxane obtainedby polycondensation of an organic alkoxysilane monomer as organic SOG.

[0007] Further, as a method of forming the insulating film, there aretwo methods including a coating method comprising coating an insulatingfilm polymer solution by e.g. spin coating to carry out film formationand a CVD method comprising plasma polymerization mainly in a plasma CVDapparatus to carry out film formation.

[0008] With respect to the characteristics of the film formation method,in the plasma CVD method, adhesion properties to a barrier metal and acopper wiring material which is a wiring material are good, on thecontrary, uniformity of the film may be problematic in some cases. Inthe coating method, although the uniformity of the film may be good,three steps of coating, solvent removal and heat treatment are required,such being economically disadvantageous as compared with the CVDmaterial, and further, adhesion properties to a barrier metal and acopper wiring material which is a wiring material, and uniform coatingitself of the coating liquid on a miniaturized substrate structure tendto be problematic in many cases.

[0009] With respect to the materials in the coating method, a method ofmaking materials be porous has been proposed so as to achieve an ultralow-k material having a dielectric constant of at most 2.5, morepreferably at most 2.0. A method of dispersing organic component fineparticles which easily decomposed into an organic or inorganic materialmatrix, followed by heat treatment to make the material be porous, and amethod of depositing SiO₂ ultrafine particles formed by evaporation ofsilicon and oxygen in a gas, to form a thin film of SiO₂ ultrafineparticles, may, for example, be mentioned.

[0010] However, although these methods of making the material be porous,are effective to achieve a low dielectric constant, mechanical strengthtends to decrease, whereby chemical mechanical polishing (CMP) may bedifficult, or increase of the dielectric constant and wiring corrosiondue to absorption of moisture may be caused in some cases.

[0011] Accordingly, the market further requires a well-balanced materialwhich satisfies all the requirements such as a low dielectric constant,an adequate mechanical strength, adhesion properties to a barrier metal,prevention of copper dispersion, plasma ashing resistance and moistureabsorption resistance. In order to satisfy these requirements to acertain extent, an organic silane type material having an increasedproportion of carbon in the organic substituent based on silane, therebyhaving characteristics intermediate between the organic polymer and theinorganic polymer has been proposed.

[0012] For example, JP-A-2000-302791 proposes a method to obtain aninterlayer insulating film not being porous and having a dielectricconstant of at most 2.4, by using a coating solution obtained byhydrolysis and polycondensation of a silicon compound having anadamantyl group by a sol-gel method in the presence of an aqueous acidsolution. However, this material is a material for the coating method,and there are still problems of the above-described film formationmethod by the film coating method.

[0013] Further, JP-A-2002-110670 discloses that a methylsilane oxidefilm is obtained by using trimethylsilane, dimethyldimethoxysilane,diethyldiethoxysilane or the like and an oxidizing agent such as oxygen,dinitrogen oxide or carbon dioxide as materials by means of a PECVDapparatus. However, as shown in Examples as described hereinafter, witha silane having only a primary short chain alkyl group, there are suchproblems that the PECVD film formation rate may be inadequate, or thecarbon uptake amount, which has a role to achieve a low dielectricconstant, tends to be small.

SUMMARY OF THE INVENTION

[0014] Under these circumstances, the present invention has been made toovercome the above problems, and it is an object of the presentinvention to provide a novel low-dielectric material, particularly amaterial for a low-dielectric constant insulating film, containing analkylsilane compound suitable for a PECVD apparatus, and to provide aninsulating film employing it and a semiconductor device containing suchan insulating film.

[0015] The present inventors have found that an organic silane compoundhaving such a structure that at least one secondary hydrocarbon groupand/or tertiary hydrocarbon group is directly bonded to a silicon atom,is suitable as a material for an insulating film, particularly alow-dielectric constant interlayer insulating film for a semiconductordevice, and the present invention has been accomplished on the basis ofthis discovery.

[0016] Namely, the present invention is to provide an insulating filmmaterial formed by chemical vapor deposition, which contains an organicsilane compound of the following formula (1):

[0017] wherein each of R¹, R² and R³ is a C₁₋₂₀ hydrocarbon group,provided that R¹, R² and R³ may be bonded to each other to form a cyclicstructure, R⁴ is a C₁₋₁₀ hydrocarbon group or a hydrogen atom, and a isan integer of from 1 to 3, an organic silane compound of the followingformula (2):

[0018] wherein each of R⁵ and R⁶ is a C₁₋₂₀ hydrocarbon group, each ofR⁷ and R⁸ is a hydrogen atom or a C₁₋₂₀ hydrocarbon group, provided thata plurality of R⁵'s, or R⁶ and R⁸ may be bonded to each other to form acyclic structure, and each of b and c is 0 or 1, or an organic silanecompound of the following formula (3):

[0019] wherein each of R⁹, R¹⁰ and R¹¹ is a C₁₋₂₀ hydrocarbon group,provided that R⁹ and R¹⁰ may be bonded to each other to form a cyclicstructure, R¹² is a C₁₋₁₀ hydrocarbon group or a hydrogen atom, d is aninteger of from 1 to 3, e is an integer of from 0 to 2, and d+e is aninteger of at most 3.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a schematic view illustrating the constitution of aPECVD apparatus.

[0021]FIG. 2 is a schematic view illustrating the constitution of IRRAS.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] In the above formula (1), each of R¹, R² and R³ is a C₁₋₂₀saturated or unsaturated hydrocarbon group, and may have any of linear,branched chain and cyclic structures. Further, a combination thereof isincluded in the present invention. If the carbon number exceeds 20, ittends to be difficult to obtain a material such as a correspondingorganic halide, or even if it can be obtained, the purity tends to below in some cases.

[0023] Taking stable use in a PECVD apparatus into consideration, aC₁₋₁₀ hydrocarbon group is particularly preferred from such a viewpointthat the vapor pressure of the organic silane compound will not be toolow.

[0024] Examples of the hydrocarbon group for each of R¹, R² and R³ arenot particularly limited, and a C₁₋₂₀, preferably C₁₋₁₀, alkyl group, anaryl group, an arylalkyl group and an alkylaryl group may be mentioned.R¹, R² and R³ may be the same or different.

[0025] As examples of a case where R¹, R² and R³ are not bonded to eachother, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl,tert-butyl, n-pentyl, tert-amyl, n-hexyl, cyclohexyl, phenyl and toluylgroup may, for example, be mentioned.

[0026] As examples of a case where R¹, R² and R³ are bonded to eachother, a 1-adamantyl group may be mentioned as a representative example.Particularly preferred as a tertiary hydrocarbon group from aneconomical viewpoint is tert-butyl wherein each of R¹, R² and R³ ismethyl, tert-amyl wherein each of R¹ and R² is methyl and R³ is ethyl,and 1-adamantyl wherein R¹, R² and R³ are bonded to one another.

[0027] R⁴ is a C₁₋₁₀ hydrocarbon group or a hydrogen atom, thehydrocarbon group is a saturated or unsaturated hydrocarbon group andmay have any of linear, branched chain and cyclic structures. If thecarbon number exceeds 10, the vapor pressure of the formed organicsilane tends to be low and its use in a PECVD apparatus tends to bedifficult in some cases, such being unfavorable.

[0028] R⁴ is preferably methyl, ethyl, n-propyl, i-propyl, n-butyl,i-butyl, sec-butyl or tert-butyl which is a C₁₋₄ hydrocarbon group, inview of preparation of the material. a is an integer of from 1 to 3.Namely, the organic silane compound of the formula (1) is atrialkoxysilane substituted with a hydrocarbon group wherein a=1, adialkoxysilane disubstituted with hydrocarbon groups wherein a=2 or analkoxysilane trisubstituted with hydrocarbon groups wherein a=3. Amixture thereof is included in the present invention.

[0029] Specific examples of the organic silane compound of the formula(1) include tert-butyltrimethoxysilane, di-tert-butyldimethoxysilane,tert-amyltrimethoxysilane, di-tert-amyldimethoxysilane,1-adamantyltrimethoxysilane, di(1-adamantyl)dimethoxysilane,tert-butyltriethoxysilane, di-tert-butyldiethoxysilane,tert-amyltriethoxysilane, di-tert-amyldiethoxysilane,1-adamantyltriethoxysilane, di(1-adamantyl)diethoxysilane,tert-butyl-tri-1-propoxysilane, di-tert-butyldi-1-propoxysilane,tert-amyl-tri-1-propoxysilane, di-tert-amyl-di-1-propoxysilane,1-adamantyl-tri-1-propoxysilane, di(1-adamantyl)di-1-propoxysilane,1-twistyl trimethoxysilane, di(1-twistyl)dimethoxysilane,1-diamantyltrimethoxysilane, di(1-diamantyl)dimethoxysilane,1-triptycyltrimethoxysilane and di(1-triptycyl)dimethoxysilane.

[0030] In the above formula (2), each of R⁵ and R⁶ is a C₁₋₂₀ saturatedor unsaturated hydrocarbon group, and may have any of linear, branchedchain and cyclic structures. Further, a combination thereof is includedin the present invention. If the carbon number exceeds 20, it tends tobe difficult to obtain a material such as a corresponding organichalide, or even if it can be obtained, the purity tends to be low insome cases.

[0031] Taking stable use in a CVD apparatus into consideration,particularly preferred is a C₁₋₁₀ hydrocarbon group. If the carbonnumber exceeds 10, the vapor pressure of the formed organic silane tendsto be low, and its use in a PECVD apparatus tends to be difficult insome cases, such being unfavorable.

[0032] Examples of the hydrocarbon group for each of R⁵ and R⁶ are notparticularly limited, and a C₁₋₂₀, preferably C₁₋₁₀ alkyl group, an arylgroup, an arylalkyl group and an alkylaryl group may be mentioned. R⁵and R⁶ may be the same or different.

[0033] As examples of a case where a plurality of R⁵'s are not bonded toeach other, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl,sec-butyl, tert-butyl, n-pentyl, tert-amyl, n-hexyl, cyclohexyl, phenyland toluyl may, for example, be mentioned.

[0034] As an example of a case where a plurality of R⁵,'s are bonded toeach other, 1-adamantyl may be mentioned as a representative example.

[0035] Each of R⁷ and R⁸ is a hydrogen atom or the same hydrocarbongroup as defined for each of R⁵ and R⁶. R⁶ and R⁸ may be bonded to eachother to form a cyclic structure, and the same example as in the abovecase where a plurality of R⁵'s are bonded to each other may bementioned.

[0036] Each of b and c is 0 or 1. Namely, when b=1 and c=0, the organicsilane compound of the formula (2) is a dialkoxysilane disubstitutedwith hydrocarbon groups, when b=0 and c=0, the compound of the formula(2) is an alkoxysilane trisubstituted with hydrocarbon groups, and whenb=0 and c=1, the compound of the formula (2) is a disiloxanehexa-substituted with hydrocarbon groups. A mixture thereof is includedin the present invention.

[0037] Specific examples of the organic silane compound of the formula(2) include:

[0038] (A) Tert-butylmethyldiethoxysilane,tert-butylmethyldimethoxysilane, tert-butylmethyldihydroxysilane,tert-butylethyldiethoxysilane, tert-butylethyldimethoxysilane,tert-butylethyldihydroxysilane, tert-butylphenyldiethoxysilane,tert-butylphenyldimethoxysilane, tert-butylphenyldihydroxysilane and thelike,

[0039] (B) 1-Adamantylmethyldiethoxysilane,1-adamantylmethyldimethoxysilane, 1-adamantylmethyldihydroxysilane,1-adamantylethyldiethoxysilane, 1-adamantylethyldimethoxysilane,1-adamantylethyldihydroxysilane, 1-adamantylphenyldiethoxysilane,1-adamantylphenyldimethoxysilane, 1-adamantylphenyldihydroxysilane andthe like,

[0040] (C) Tert-butyldimethylhydroxysilane,tert-butyldimethylmethoxysilane, tert-butyldimethylethoxysilane,tert-butyldiethylhydroxysilane, tert-butyldiethylmethoxysilane,tert-butyldiethylethoxysilane, tert-butyldiphenylhydroxysilane,tert-butyldiphenylmethoxysilane, tert-butyldiphenylethoxysilane and thelike,

[0041] (D) 1-Adamantyldimethyl hydroxysilane,1-adamantyldimethylmethoxysilane, 1-adamantyldimethylethoxysilane,1-adamantyldiethylhydroxysilane, 1-adamantyldiethylmethoxysilane,1-adamantyldiethylethoxysilane, 1-adamantyldiphenylhydroxysilane,1-adamantyldiphenylmethoxysilane, 1-adamantyldiphenylethoxysilane andthe like,

[0042] (E) 1,3-Di-tert-butyl-1,1,3,3-tetramethyldisiloxane,1,3-di-tert-butyl-1,1,3,3-tetraethyldisiloxane,1,3-di-tert-butyl-1,1,3,3-tetraphenyldisiloxane and the like, and

[0043] (F) 1,3-Di(1-adamantyl)-1,1,3,3-tetramethyldisiloxane,1,3-di(1-adamantyl)-1,1,3,3-tetraethyldisiloxane,1,3-di(1-adamantyl)-1,1,3,3,-tetraphenyldisiloxane and the like.

[0044] In the above formula (3), each of R⁹, R¹⁰ and R¹¹ is a C₁₁₂₀saturated or unsaturated hydrocarbon group, and may have any of linear,branched chain and cyclic structures. Further, a combination thereof isincluded in the present invention. If the carbon number exceeds 20, ittends to be difficult to obtain a material such as a correspondingorganic halide, or even if it can be obtained, the purity tends to below in some cases.

[0045] Taking stable use in a CVD apparatus into consideration,particularly preferred is a C₁₋₁₀ hydrocarbon group from such aviewpoint that the vapor pressure of the organic silane compound willnot be too low.

[0046] Examples of the hydrocarbon group for each of R⁹, R¹⁰ and R¹¹ arenot particularly limited, and a C₁₋₂₀, preferably C₁₋₁₀ alkyl group, anaryl group, an arylalkyl group, and an alkylaryl group may be mentioned.R⁹, R¹⁰ and R¹¹ may be the same or different.

[0047] As examples of a case where R⁹ and R¹⁰ are not bonded to eachother, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl,tert-butyl, n-pentyl, tert-amyl, n-hexyl, cyclohexyl, phenyl and toluylgroups may, for example, be mentioned.

[0048] As examples of a group wherein R⁹ and R¹⁰ are bonded to eachother and bonded to Si by means of a tertiary carbon, cyclobutyl,cyclobutenyl, cyclopentyl, cyclopentadienyl, cyclohexyl, cyclohexenyl,cyclooctenyl and cyclooctadienyl groups are mentioned as representativeexamples. Particularly preferred from an economical viewpoint are aniso-propyl group wherein each of R⁹ and R¹⁰ is methyl, a sec-butyl groupwherein R⁹ and R¹⁰ are methyl and ethyl, and cyclopentyl,cyclopentadienyl, cyclohexyl and cyclohexenyl groups wherein R⁹ and R¹⁰are bonded to each other.

[0049] R¹² is a C₁₋₁₀ hydrocarbon group or a hydrogen atom, and thehydrocarbon group is a saturated or unsaturated hydrocarbon group, andmay have any of linear, branched chain and cyclic structures. If thecarbon number exceeds 10, the vapor pressure of the formed organicsilane tends to be low, and its use in a PECVD apparatus tends to bedifficult in some cases, such being unfavorable.

[0050] Preferred as R¹² are methyl, ethyl, n-propyl, i-propyl, n-butyl,i-butyl, sec-butyl and tert-butyl which are C₁₋₄ hydrocarbon groups, inview of preparation of the material.

[0051] d in an integer of from 1 to 3, e is an integer of from 0 to 2,and d+e is an integer of at most 3. Namely, the organic silane compoundof the formula (3) is a trialkoxysilane substituted with a hydrocarbongroup wherein d=1 and e=0, a dialkoxysilane disubstituted withhydrocarbon groups wherein d=1 and e=1, or d=2 and e=0, or analkoxysilane trisubstituted with hydrocarbon groups wherein (d=1, e=2),(d=2, e=1) or (d=3, e=0). A mixture thereof is included in the presentinvention.

[0052] Specific examples of the organic silane compound of the formula(3) include:

[0053] (G) Iso-propyltrimethoxysilane, diiso-propyldimethoxysilane,triiso-propylmethoxysilane, iso-propylmethyldimethoxysilane,iso-propylethyldimethoxysilane, isopropylphenyldimethoxysilane,iso-propyldimethylmethoxysilane, iso-propyldiethylmethoxysilane andiso-propyldiphenylmethoxysilane,

[0054] (H) Iso-propyl triethoxysilane, diiso-propyldiethoxysilane,triiso-propylethoxysilane, iso-propylmethyldiethoxysilane,iso-propylethyldiethoxysilane, iso-propylphenyldiethoxysilane,iso-propyldimethylethoxysilane, iso-propyldiethylethoxysilane andiso-propyldiphenylethoxysilane,

[0055] (I) Sec-butyl trimethoxysilane, disec-butyldimethoxysilane,trisec-butylmethoxysilane, sec-butylmethyldimethoxysilane,sec-butylethyldimethoxysilane, sec-butylphenyldimethoxysilane,sec-butyldimethylmethoxysilane, sec-butyldiethylmethoxysilane andsec-butyldiphenylmethoxysilane,

[0056] (J) Sec-butyl triethoxysilane, disec-butyldiethoxysilane,trisec-butylethoxysilane, sec-butylmethyldiethoxysilane,sec-butylethyldiethoxysilane, sec-butylphenyldiethoxysilane,sec-butyldimethylethoxysilane, sec-butyldiethylethoxysilane andsec-butyldiphenylethoxysilane,

[0057] (K) Cyclopentyl trimethoxysilane, dicyclopentyldimethoxysilane,tricyclopentylmethoxysilane, cyclopentylmethyldimethoxysilane,cyclopentylethyldimethoxysilane, cyclopentylphenyldimethoxysilane,cyclopentyldimethylmethoxysilane, cyclopentyldiethylmethoxysilane andcyclopentyldiphenylmethoxysilane,

[0058] (L) Cyclopentyltriethoxysilane, dicyclopentyldiethoxysilane,tricyclopentylethoxysilane, cyclopentylmethyldiethoxysilane,cyclopentylethyldiethoxysilane, cyclopentylphenyldiethoxysilane,cyclopentyldimethylethoxysilane, cyclopentyldiethylethoxysilane andcyclopentyldiphenylethoxysilane,

[0059] (M) Cyclopentadienyltrimethoxysilane,dicyclopentadienyldimethoxysilane, tricyclopentadienylmethoxysilane,cyclopentadienylmethyldimethoxysilane,cyclopentadienylethyldimethoxysilane,cyclopentadienylphenyldimethoxysilane,cyclopentadienyldimethylmethoxysilane,cyclopentadienyldiethylmethoxysilane andcyclopentadienyldiphenylmethoxysilane,

[0060] (N) Cyclopentadienyltriethoxysilane,dicyclopentadienyldiethoxysilane, tricyclopentadienylethoxysilane,cyclopentadienylmethyldiethoxysilane,cyclopentadienylethyldiethoxysilane,cyclopentadienylphenyldiethoxysilane,cyclopentadienyldimethylethoxysilane,cyclopentadienyldiethylethoxysilane andcyclopentadienyldiphenylethoxysilane,

[0061] (O) Cyclohexyltrimethoxysilane, dicyclohexyldimethoxysilane,tricyclohexylmethoxysilane, cyclohexylmethyldimethoxysilane,cyclohexylethyldimethoxysilane, cyclohexylphenyldimethoxysilane,cyclohexyldimethylmethoxysilane, cyclohexyldiethylmethoxysilane andcyclohexyldiphenylmethoxysilane,

[0062] (P) Cyclohexyltriethoxysilane, dicyclohexyldiethoxysilane,tricyclohexylethoxysilane, cyclohexylmethyldiethoxysilane,cyclohexylethyldiethoxysilane, cyclohexylphenyldiethoxysilane,cyclohexyldimethylethoxysilane, cyclohexyldiethylethoxysilane andcyclohexyldiphenylethoxysilane,

[0063] (O) Cyclohexenyltrimethoxysilane, dicyclohexenyldimethoxysilane,tricyclohexenylmethoxysilane, cyclohexenylmethyldimethoxysilane,cyclohexenylethyldimethoxysilane, cyclohexenylphenyldimethoxysilane,cyclohexenyldimethylmethoxysilane, cyclohexenyldiethylmethoxysilane andcyclohexenyldiphenylmethoxysilane, and

[0064] (R) Cyclohexenyltriethoxysilane, dicyclohexenyldiethoxysilane,tricyclohexenylethoxysilane, cyclohexenylmethyldiethoxysilane,cyclohexenylethyldiethoxysilane, cyclohexenylphenyldiethoxysilane,cyclohexenyldimethylethoxysilane, cyclohexenyldiethylethoxysilane andcyclohexenyldiphenylethoxysilane.

[0065] The method for producing the organic silane compound of the aboveformula (1) is not particularly limited. For example, the organic (1) isnot formula (1) can be produced by reacting organic lithium having atertiary carbon atom and a lithium atom directly bonded to each other,produced by reacting an organic halide of the following formula (4):

[0066] wherein each of R¹ to R³ is as defined above, and X is a chlorineatom, a bromine atom or an iodine atom, with metal lithium particles,with a halogenated alkoxysilane (m=1−3) or a tetraalkoxysilane (m=0) ofthe following formula (5):

X′_(m)Si(OR⁴)_(4−m)  (5)

[0067] wherein R⁴ is as defined above, X′ is a fluorine atom, a chlorineatom, a bromine atom or an iodine atom, and m is an integer of from 0 to3. Examples of the organic halide of the formula (4) include tert-butylchloride, tert-butyl bromide, tert-butyl iodide, tert-amyl chloride,tert-amyl bromide, tert-amyl iodide, 1-adamantyl chloride, 1-adamantylbromide, 1-adamantyl iodide, 1-twistyl chloride, 1-twistyl bromide,1-twistyl iodide, 1-diamantyl chloride, 1-diamantyl bromide, 1-diamantyliodide, 1-triptycyl chloride, 1-triptycyl bromide and 1-triptycyliodide.

[0068] Examples of the halogenated alkoxysilane or tetraalkoxysilane ofthe formula (5) include chlorotrimethoxysilane, dichlorodimethoxysilane,trichloromethoxysilane, tetramethoxysilane, chlorotriethoxysilane,dichlorodiethoxysilane, trichloroethoxysilane, tetramethoxysilane,tetraethoxysilane, tetrapropoxysilane, chlorotri-1-propoxysilane,dichlorodi-1-propoxysilane, trichloro-1-propoxysilane,tetra-1-propoxysilane, tetrabutoxysilane, tetra-1-butoxysilane,tetra-sec-butoxysilane and tetra-tert-butoxysilane.

[0069] By employing the present production method, high purity organicsilane compound of the formula (1) can be obtained with a highpercentage of yield while suppressing formation of by-products.Particularly, an organic silane compound having at least two structuresin which a tertiary carbon atom is directly bonded to a silicon atom,can be produced, which can hardly be produced industrially by otherproduction methods of using e.g. organic magnesium.

[0070] The conditions of the reaction of the organic halide of the aboveformula (4) and metal lithium particles are not particularly limited,and one example is shown below. As the metal lithium to be used, e.g. alithium wire, a lithium ribbon or a lithium shot may, for example, beemployed, and it is preferred to employ lithium fine particles having aparticle size of at most 500 μm in view of reaction efficiency.

[0071] The solvent to be used for the reaction of the organic halidewith the metal lithium particles is not particularly limited so long asit is used for said technical field. For example, a saturatedhydrocarbon such as n-pentane, i-pentane, n-hexane, cyclohexane,n-heptane or n-decane, an unsaturated hydrocarbon such as toluene,xylene or decene-1, or an ether such as diethyl ether, propyl ether ordibutyl ether may be used.

[0072] The reaction temperature for the reaction of the organic halidewith the metal lithium particles is preferably such a temperature rangethat the formed organic lithium having a tertiary carbon atom andlithium are directly bonded to each other will not decompose. Thereaction is preferably carried out usually at a temperature of from −100to 200° C. which is industrially employed, preferably at a temperatureof from −85 to 150° C. As the pressure condition of the reaction, thereaction may be carried out under elevated pressure, normal pressure orreduced pressure.

[0073] The prepared organic lithium having a tertiary carbon atom and alithium atom directly bonded to each other may be used as it is afterthe production, or it may be used after unreacted organic halide andmetal lithium, and lithium halide as a reaction by-product are removed.

[0074] The conditions of the reaction of the organic lithium having atertiary carbon atom and a lithium atom directly bonded to each otherand the halogenated alkoxysilane or tetraalkoxysilane of the aboveformula (3), are not particularly limited, and one example is shownbelow.

[0075] The reaction solvent to be used may be the same solvent as oneused for the above reaction of the organic halide with the metal lithiumparticles. The reaction temperature is preferably such a temperaturerange that the organic lithium having a tertiary carbon atom and lithiumdirectly bonded to each other to be used will not decompose. Thereaction is preferably carried out usually at a temperature of from −100to 200° C. which is industrially employed, preferably at a temperatureof from −85 to 150° C. As the pressure condition of the reaction, thereaction may be carried out under elevated pressure, normal pressure orreduced pressure.

[0076] The method for producing the organic silane of the above formula(2) is not particularly limited. For example, a dialkoxysilanedisubstituted with hydrocarbon groups of the following formula (9) whichis the compound of the above formula (2) wherein b=1 and c=0:

[0077] wherein each of R⁵, R⁷ and R⁸ is as defined for the above formula(2), or an alkoxysilane trisubstituted with hydrocarbon groups of thefollowing formula (10) which is the compound of the formula (2) whereinb=0 and c=0:

[0078] wherein each of R⁵, R⁷ and R⁸ is as defined for the above formula(2), can be produced by reacting an organic lithium compound or anorganic magnesium compound of the following formula (11):

[0079] wherein R⁵ is as defined for the above formula (2), and M is Li,MgCl, MgBr or MgI, with a halogenated silane substituted with ahydrocarbon group or an alkoxysilane substituted with a hydrocarbongroup of the following formula (12):

Z_(f)SiR⁵ _(g)[(O)_(b)R⁷]_(h)(OR⁸)_(4−(f+g+h))  (12)

[0080] wherein each of R⁵, R⁷, R⁸ and b is as defined for the aboveformula (2), Z is a fluorine atom, a chlorine atom, a bromine atom or aniodine atom, f is an integer of from 0 to 3, g is an integer of from 0to 2, h is an integer of from 0 to 2 when b=0, or an integer of from 0to 4 when b=1, and f+g+h is from 0 to 4.

[0081] The method for producing a disiloxane hexa-substituted withhydrocarbon groups of the above formula (2) wherein c=1 is notparticularly limited, and it can be produced by dimerization of theobtained dialkoxysilane disubstituted with hydrocarbon groups oralkoxysilane trisubstituted with hydrocarbon groups in the presence ofwater and an acid.

[0082] Further, after the preparation reaction, in a case where ahalogen atom directly bonded to silicon remains in the alkoxysilanesubstituted with a hydrocarbon group as a reaction product, an alkalimetal alkoxide of the following formula (13):

R⁸OM′  (13)

[0083] wherein M′ is an alkali metal, and R⁸ is as defined for the aboveformula (2), may be reacted therewith for alkoxylation.

[0084] Examples of the alkali metal alkoxide of the above formula (13)include lithium methoxide, lithium ethoxide, lithium-1-propoxide, sodiummethoxide, sodium ethoxide, sodium-1-propoxide, potassium methoxide,potassium ethoxide and potassium-1-propoxide.

[0085] By employing the present production method, high purity organicsilane compound of the formula (1) can be obtained with a highpercentage of yield while suppressing formation of by-products.

[0086] The organic lithium compound or organic magnesium compound of theabove formula (11) used for production can be produced by reacting anorganic halide with metal lithium particles or metal magnesium.

[0087] The conditions of the reaction of the organic halide with metallithium particles or metal magnesium to prepare the organic lithiumcompound or organic magnesium compound of the above formula (11) are notparticularly limited, and one example is shown below.

[0088] As the metal lithium to be used, a lithium wire, a lithium ribbonor a lithium shot may, for example, be employed, and it is preferred toemploy lithium fine particles having a particle size of at most 500 μmin view of reaction efficiency.

[0089] As the metal magnetism to be used, magnesium ribbon, magnesiumparticles or magnesium powder may, for example, be used.

[0090] The solvent to be used for the above reaction is not particularlylimited so long as it is used in said technical field, and for example,a saturated hydrocarbon such as n-pentane, i-pentane, n-hexane,cyclohexane, n-heptane or n-decane, an unsaturated hydrocarbon such astoluene, xylene or decene-1, or an ether such as diethyl ether, dipropylether, tert-butyl methyl ether, dibutyl ether or cyclopentyl methylether may be used. Further, a solvent mixture thereof may also be used.

[0091] The reaction temperature for the above reaction is preferablysuch a temperature range that the formed organic lithium or organicmagnesium will not decompose. The reaction is preferably carried outusually at a temperature of from −100 to 200° C. which is industriallyemployed, preferably at a temperature of from −85 to 150° C. As thepressure condition of the reaction, the reaction may be carried outunder elevated pressure, normal pressure or reduced pressure.

[0092] The prepared organic lithium or organic magnesium may be used asit is after prepration, or may be used after unreacted organic halideand metal lithium or metal magnesium, and lithium halide or magnesiumhalide as a reaction by-product are removed.

[0093] The conditions of the reaction of the organic lithium or organicmagnesium with the halogenated silane substituted with a hydrocarbongroup or alkoxysilane substituted with a hydrocarbon group of the aboveformula (12) are not particularly limited, and one example is shownbelow.

[0094] The reaction solvent to be used may be the same solvent as oneused for the above reaction of the organic halide with metal lithium ormetal magnesium. The reaction temperature is preferably such atemperature range that the organic lithium or organic magnetism to beused will not decompose. The reaction is carried out usually at atemperature of from −100 to 200° C. which is industrially employed,preferably at a temperature of from −85 to 150° C. As the pressurecondition of the reaction, the reaction may be carried out underelevated pressure, normal pressure or reduced pressure.

[0095] The reaction condition of the alkali metal alkoxide of the aboveformula (13) in the case where a halogen atom directly bonded to siliconremains, are not particularly limited, and the reaction can be carriedout under the same conditions of the above reaction of the organiclithium or organic magnesium with the halogenated alkoxysilane ortetraalkoxysilane.

[0096] The method for producing the organic silane compound of the aboveformula (3) is not particularly limited. For example, the organic silanecompound of the formula (3) can be produced by reacting a compoundhaving a secondary carbon atom and a lithium atom directly bonded toeach other, produced by reacting an organic compound of the followingformula (6):

[0097] wherein each of R⁹ and R¹⁰ is as defined above, and Y is ahydrogen atom, a chlorine atom, a bromine atom or an iodine atom, withorganic lithium or metal lithium particles, with a halogenated silane, ahalogenated alkoxysilane or a tetraalkoxysilane of the following formula(7):

Y′_(p)SiR¹¹ _(q)(OR¹²)_(4−(p+q))  (7)

[0098] wherein Y′ is a fluorine atom, a chlorine atom, a bromine atom oran iodine atom, each of R¹¹ and R¹² is as defined above, p is an integerof from 0 to 4, q is an integer of from 0 to 2, and p+q is an integer ofat most 4.

[0099] Further, with respect to the above production method, a methodfor producing the organic silane compound of the formula (3) by usingmetal magnesium instead of the organic lithium or metal lithiumparticles is also included in the present invention.

[0100] Examples of the organic compound of the formula (6) wherein Y isa chlorine atom, a bromine atom or an iodine atom include iso-propylchloride, iso-propyl bromide, iso-propyl iodide, sec-butyl chloride,sec-butyl bromide, sec-butyl iodide, cyclopentyl chloride, cyclopentylbromide, cyclopentyl iodide, cyclohexyl chloride, cyclohexyl bromide andcyclohexyl iodide.

[0101] Further, examples of the organic compound of the formula (6)wherein Y is a hydrogen atom include cyclopentadiene,pentamethylcyclopentadiene and 1,2,3,4-tetramethyl-1,3-cyclopentadiene,and by reacting organic lithium such as n-butyl lithium or tert-butyllithium with such a compound, a compound having a secondary carbon atomand a lithium atom directly bonded to each other can be produced.

[0102] Examples of the halogenated silane, halogenated alkoxysilane ortetraalkoxysilane of the formula (7) include tetrachlorosilane,chlorotrimethoxysilane, dichlorodimethoxysilane, trichloromethoxysilane,tetramethoxysilane, chlorotriethoxysilane, dichlorodiethoxysilane,trichloroethoxysilane, tetramethoxysilane, tetraethoxysilane,tetrapropoxysilane, chlorotri-1-propoxysilane,dichlorodi-1-propoxysilane, trichloro-1-propoxysilane,tetra-1-propoxysilane, tetrabutoxysilane, tetra-1-butoxysilane,tetra-sec-butoxysilane, tetra-tert-butoxysilane, methyltrimethoxysilane,dimethyldimethoxysilane, ethyltrimethoxysilane, diethyldiethoxysilane,vinyltriethoxysilane, vinyltrimethoxysilane, vinyltrichlorosilane,divinyldichlorosilane, phenyltrimethoxysilane anddiphenyldimethoxysilane.

[0103] Further, after the preparation reaction, in a case where ahalogen atom directly bonded to silicon remains in the alkoxysilanesubstituted with a hydrocarbon group as a reaction product, an alkalimetal alkoxide of the following formula (8):

R¹²OM  (8)

[0104] wherein M is an alkali metal, and R¹² is as defined above, may bereacted for alkoxylation.

[0105] Examples of the alkali metal alkoxide of the above formula (8)include lithium methoxide, lithium ethoxide, lithium-1-propoxide, sodiummethoxide, sodium ethoxide, sodium-1-propoxide, potassium methoxide,potassium ethoxide and potassium-1-propoxide.

[0106] By employing the present production method, high purity organicsilane compound of the formula (3) can be obtained with a highpercentage of yield while suppressing the formation of by-products.

[0107] The conditions for production of the compound having a secondarycarbon atom and a lithium atom (or a magnesium atom) directly bonded toeach other are not particularly limited, and one example is shown below.

[0108] As the metal lithium to be used, a lithium wire, a lithium ribbonor a lithium shot may, for example, be employed, and it is preferred toemploy lithium fine particles having a particle size of at most 500 μmin view of reaction efficiency.

[0109] As the metal magnetism to be used, magnesium ribbon, magnesiumparticles or magnetism powder may, for example, be employed.

[0110] As the organic lithium to be used, a n-hexane solution ofn-butyllithium or n-pentane solution of tert-butyllithium may, forexample, be used.

[0111] The solvent to be used for the above reaction is not particularlylimited so long as it is used in said technical field. For example, asaturated hydrocarbon such as n-pentane, i-pentane, n-hexane,cyclohexane, n-heptane or n-decane, an unsaturated hydrocarbon such astoluene, xylene or decene-1, or an ether such as diethyl ether, dipropylether, tert-butyl methyl ether, dibutyl ether or cyclopentyl methylether may be used. Further, a solvent mixture thereof may also be used.

[0112] The reaction temperature for the above reaction is preferablysuch a temperature range that the formed compound having a secondarycarbon atom and a lithium atom bonded to each other, or compound havinga secondary carbon atom and a magnesium atom directly bonded to eachother, will not decompose. The reaction is preferably carried outusually at a temperature of from −100 to 200° C. which is industriallyemployed, preferably at a temperature of from −85 to 150° C. As thepressure condition of the reaction, the reaction may be carried outunder elevated pressure, normal pressure or reduced pressure.

[0113] The prepared compound having a secondary carbon atom and alithium atom directly bonded to each other or compound having asecondary carbon atom and a magnesium atom directly bonded to eachother, may be used as it is after the production, or it may be usedafter unreacted organic halide and metal lithium or metal magnesium, andlithium halide or magnesium halide as a reaction by-product are removed.

[0114] The conditions of the reaction of the compound having a secondarycarbon atom and a lithium atom directly bonded to each other or thecompound having a secondary carbon atom and a magnesium atom directlybonded to each other, thus obtained, with the halogenated silane,halogenated alkoxysilane or tetraalkoxysilane of the above formula (3),are not particularly limited, and one example is shown below.

[0115] The reaction solvent to be used may be the same solvent as oneused for the above reaction of the compound having a secondary carbonatom and a lithium atom (or a magnesium atom) directly bonded to eachother. The reaction temperature is preferably such a temperature rangethat the compound having a secondary carbon atom and a lithium atom (ora magnesium atom) directly bonded to each other will not decompose. Thereaction is preferably carried out usually at a temperature of from −100to 200° C. which is industrially employed, preferably at a temperatureof from −85 to 150° C. As the pressure condition of the reaction, thereaction may be carried out under elevated pressure, normal pressure orreduced pressure.

[0116] As a purification method of the formed organic silane compound ofeach of the formulae (1) to (3), in order to achieve a water content ofless than 50 ppm and an amount of impurities derived from productionmaterials, other than the elements of silicon, carbon, oxygen andhydrogen, of less than 10 ppb, which are effective for use as aninsulating film material, lithium salt, magnesium salt and alkali metalsalt which are by-products should be removed by means such as filtrationby using a glass filter, a sintered porous body or the like,distillation under normal pressure or reduced pressure, or purificationby column separation using silica, alumina or high polymer gel. At thistime, these means may be combined as the case requires. In a method ofextracting lithium salt, magnesium salt and alkali metal salt which areby-products with e.g. water, which has been employed in a conventionalorganic synthesis technology, the finally obtained organic silanecompound of the formula (1) has a large amount of moisture andimpurities other than the elements of silicon, carbon, oxygen andhydrogen, particularly metal impurity residue, and is inappropriate asan insulating film material in some cases.

[0117] Further, in a case where a by-product containing a silanolstructure is formed, hydroxyl groups of the silanol are precipitated ina form of a sodium salt or a potassium salt with e.g. sodium hydride orpotassium hydride, and then the alkoxysilane substituted with ahydrocarbon group as the main product can be isolated by distillation.

[0118] For production, the operation is carried out in accordance with amethod in the field of said organic metal compound prepration. Namely,it is preferred that the reaction is carried out in an atmosphere ofdehydrated and deoxidized nitrogen or argon, and a solvent, a columnbulking agent for purification, etc., to be used are preliminarilysubjected to dehydration operation. Further, it is preferred thatimpurities such as metal residue and particles are removed.

[0119] The organic silane compounds of the formulae (1) to (3) of thepresent invention are materials suitable as a low-dielectric constantinsulating material for film formation by a PECVD apparatus.

[0120] It is also possible to obtain a low-dielectric constantinsulating material having a decreased dielectric constant in such amanner that the above material is formed into a film by CVD, followed byheat treatment at a temperature of at least 350° C. at which thetertiary carbon atom and the silicon atom are separated, and theseparated hydrocarbon molecule is discharged out of the film topurposely form pores of a molecule size in the film so that the filmbecomes porous.

[0121] The low-dielectric constant insulating film material of thepresent invention is suitable for production of ULSI employingmultilevel interconnection, and the present invention further provides asemiconductor device employing the insulating film.

[0122] Now, the present invention will be described in detail withreference to Examples. However, it should be understood that the presentinvention is by no means restricted to such specific Examples.

EXAMPLE 1

[0123] Preparation of Organic Lithium Having a Tertiary Carbon Atom anda Lithium Atom Directly Bonded to Each Other

[0124] 1.40 g (0.200 mol) of Li particles having an average particlesize of 150 um and 100 ml of dry pentane were charged in a 200 mlSchlenk tube reactor equipped with a dropping funnel in a stream ofnitrogen, and a solution having 21.5 g (0.100 mol) of 1-bromoadamantanedissolved in 50 ml of n-pentane was dropwise added thereto from thedropping funnel with stirring at 30° C. while keeping the internaltemperature at 30° C., followed by stirring for 14 hours under reflux ofn-pentane.

[0125] After completion of the reaction, unreacted metal Li andby-product LiBr were removed by filtration to obtain a n-pentanesolution of 1-adamantyl lithium.

[0126] Preparation of Organic Silane Compound Having Such a StructureThat a Tertiary Carbon Atom is Directly Bonded to a Silicon Atom

[0127] 50 ml of dry pentane and 13.7 g (0.090 mol) of tetramethoxysilanewere charged in a 200 ml Schlenk tube reactor equipped with a droppingfunnel, and the above prepared n-pentane solution of 1-adamantyl lithiumwas dropwise added thereto from the dropping funnel while keeping theinternal temperature at 0° C. After completion of the dropwise addition,stirring was carried out at room temperature for 2 hours. Aftercompletion of the reaction, n-pentane was distilled off, and the aimedproduct 1-adamantyltrimethoxysilane was purified by isolation by meansof column chromatography. The percentage of yield was 82%.

EXAMPLE 2

[0128] The same operation as in Example 1 was carried out except that6.85 g (0.045 mol) of tetramethoxysilane was used instead of 13.7 g(0.090 mol) to obtain the aimed product di(1-adamantyl)dimethoxysilane.The percentage of yield was 71%.

COMPARATIVE EXAMPLE 1

[0129] Preparation of Organic Magnesium Having a Tertiary Carbon Atomand a Lithium Atom Directly Bonded to Each Other

[0130] 21.4 g (0.880 mol) of magnesium and 125.0 g (0.960 mol) ofdibutyl ether were charged in a 1,000 ml flask equipped with a refluxcondenser, a dropping funnel and a stirring apparatus, in an atmosphereof nitrogen, and after stirring was started, a solution having 172.1 g(0.800 mol) of 1-bromoadamantane and 4.36 g (0.0400 mol) of ethylbromide diluted with 250.0 g (1.92 mol) of dibutyl ether was dropwiseadded thereto from the dropping funnel over a period of 2 hours underreflux of dibutyl ether, and then stirring was carried out for 4 hoursunder reflux of dibutyl ether, to obtain a dibutyl ether solution of1-adamantyl magnesium bromide.

[0131] Preparation of Organic Silane Compound Having Such a StructureThat a Tertiary Carbon is Directly Bonded to a Silicon Atom

[0132] 200 ml of dry dibutyl ether and 54.8 g (0.360 mol) oftetramethoxysilane were charged in a 2,000 ml reactor equipped with areflux condenser and a stirring apparatus in an atmosphere of nitrogen,and the above prepared dibutyl ether solution of 1-adamantyl magnesiumbromide was dropwise added thereto by a rotary pump while keeping theinternal temperature at 0° C. After completion of the dropwise addition,stirring was carried out at room temperature for 2 hours.

[0133] The product was confirmed by means of gas chromatography,whereupon no formation of the aimed productdi(1-adamantyl)dimethoxysilane was confirmed. Stirring was furthercarried out for 2 hours under reflux of dibutyl ether, but no formationof di(1-adamantyl)dimethoxysilane was confirmed.

EXAMPLE 3

[0134] Preparation of Organic Lithium Having a Tertiary Carbon Atom anda Lithium Atom Directly Bonded to Each Other

[0135] 1.39 g (0.200 mol) of Li particles having an average particlesize of 75 μm and 50 ml of dry pentane were charged in a 200 ml Schlenktube reactor equipped with a reflux condenser and a dropping funnel in astream of argon, and a solution having 3.41 g (0.020 mol) of1-chloroadamantane dissolved in 50 ml of n-pentane was dropwise addedthereto from the dropping funnel with stirring at 30° C. while keepingthe internal temperature at 30° C. Stirring was carried out further for8 hours under reflux of n-pentane, and then it was confirmed that no1-chloroadamantane as the material was detected, and a n-pentanesolution of 1-adamantyl lithium was obtained.

[0136] Preparation of Organic Silane Compound Having Such a StructureThat a Tertiary Carbon Atom is Directly Bonded to a Silicon Atom

[0137] 50 ml of dry n-pentane and 3.33 g (0.016 mol) oftetraethoxysilane were charged in a 200 ml Schlenk tube reactor equippedwith a reflux condenser and a dropping funnel in an atmosphere of argon,and the above prepared n-pentane solution of 1-adamantyl lithium wasdropwise added thereto from the dropping funnel at room temperature.After completion of the dropwise addition, stirring was carried out for5 hours under reflux of n-pentane. After completion of the reaction,n-pentane was distilled off, and the aimed product1-adamantyltriethoxysilane was purified by isolation by means of columnchromatography. The percentage of yield was 72%.

EXAMPLE 4

[0138] The same operation as in Example 3 was carried out except that2.44 g (0.016 mol) of tetramethoxysilane was used instead oftetraethoxysilane to obtain the aimed product1-adamantyltrimethoxysilane. The percentage of yield was 78%.

COMPARATIVE EXAMPLE 2

[0139] Preparation of Organic Magnesium Having a Tertiary Carbon Atomand a Magnesium Atom Directly Bonded to Each Other

[0140] 2.92 g (0.120 mol) of magnesium and 30 ml of dibutyl ether werecharged in a 200 ml Schlenk tube equipped with a reflux condenser, adropping funnel and a stirring apparatus in an atmosphere of nitrogen,and a solution having 21.5 g (0.100 mol) of 1-bromoadamantane and 1.09 g(0.0100 mol) of ethyl bromide dissolved in 40 ml of dibutyl ether wasdropwise added thereto from the dropping funnel at 80° C. over a periodof 1 hour, and stirring was carried out further for 2 hours at 120° C.to obtain a dibutyl ether solution of 1-adamantyl magnesium bromide.

[0141] Preparation of Organic Silane Compound Having such a StructureThat a Tertiary Carbon Atom is Directly Bonded to a Silicon Atom

[0142] To the above dibutyl ether solution of 1-adamantyl magnesiumbromide in the 200 ml Schlenk tube, a solution having 16.7 g (0.080 mol)of tetraethoxysilane dissolved in 20 ml of dry dibutyl ether wasdropwise added from the dropping funnel at 45° C. over a period of 10minutes. After completion of the dropwise addition, stirring was carriedout at 120° C. for 6 hours.

[0143] The reaction liquid was analyzed by means of a gas chromatographymass spectrometer (GC-MS), and no formation of1-adamantyltriethoxysilane or di(1-adamantyl)diethoxysilane wasconfirmed at all.

EXAMPLE 5

[0144] Preparation of Organic Silane Compound Having Such a StructureThat a Tertiary Carbon Atom is Directly Bonded to a Silicon Atom

[0145] 50.0 g (0.240 mol) of tetraethoxysilane and 250 ml of n-pentanewere charged in a 500 ml four-necked flask reactor equipped with areflux condenser, a dropping funnel and a stirring apparatus in anatmosphere of nitrogen, and cooled to 0° C. 78.0 g (0.289 mol) of an-pentane solution of 23.7 wt % tert-butyllithium was dropwise addedthereto from the dropping funnel over a period of 1 hour, and stirringwas carried out further for 2 hours.

[0146] The percentage of yield of tert-butyltriethoxysilane was 93.0% bya gas chromatography internal standard method.

[0147] Lithium ethoxide was removed by filtration from the reactionliquid, and n-pentane was distilled off from the filtrate, followed bydistillation under reduced pressure to isolatetert-butyltriethoxysilane. The yield was 39.6 g, and the percentage ofisolated yield was 74.8%.

[0148] The results of analysis of the isolated tert-butyltriethoxysilaneby ¹H-NMR, ¹³C-NMR and GC-MS were as follows, and it was shown that theaimed product had a high purity.

[0149]¹H-NMR (CDCl₃): 1.025 ppm (s, 9H), 1.285 ppm (t, 9H) 3.915 ppm (q,6H)

[0150]¹³C-NMR (CDCl₃) 17.583 ppm, 18.426 ppm, 26.391 ppm, 58.785 ppm

[0151] GC-MS: Mw=220, C₁₀H₂₄O₃Si

[0152] Further, the water content and the lithium content in 100 g ofthe obtained tert-butyltriethoxysilane were measured by means of a KarlFischer moisture meter and ICP-MS (inductively coupled plasma massspectrometer, manufactured by Yokogawa Analytical Systems, Inc.,tradename “HP4500”) and as a result, H₂O=17 ppm and Li<10 ppb, and theobtained product was useful as an insulating film material.

COMPARATIVE EXAMPLE 3

[0153] Preparation of an Organic Silane Compound Having Such a Structurethat a Tertiary Carbon Atom is Directly Bonded to a Silicone Atom

[0154] 11.8 g (0.0567 mol) of tetraethoxysilane and 50 ml oftetrahydrofuran were charged in a 500 ml four-necked flask reactorequipped with a reflux condenser, a dropping funnel and a stirringapparatus in an atmosphere of nitrogen, and cooled to 0° C. 40 ml(0.0680 mol) of a tetrahydrofuran solution of 1.70 mol/L tert-butylmagnesium chloride was dropwise added thereto from the dropping funnelover a period of 1 hour, and stirring was carried out for 2 hours. Partof the reaction liquid was collected to carry out gas chromatography,but no formation of tert-butyltriethoxysilane was confirmed.

[0155] Stirring was carried out further for 3 hours at room temperatureto conduct reaction, but no formation of tert-butyltriethoxysilane wasconfirmed.

[0156] Stirring was carried out further for 3 hours under reflux oftetrahydrofuran to conduct reaction. The percentage of yield oftert-butyltriethoxysilane was 1.4% by a gas chromatography internalstandard method, and it was found that the aimed product can notefficiently be prepared by the reaction of tert-butyl magnesium chloridewith tetraethoxysilane.

EXAMPLE 6

[0157] Preparation of Organic Silane Compound Having Such a StructureThat a Tertiary Carbon Atom is Directly Bonded to a Silicon Atom

[0158] The same operation as in Example 5 was carried out except that36.6 g (0.240 mol) of tetramethoxysilane was used instead oftetraethoxysilane to obtain the aimed producttert-butyltrimethoxysilane. As a result, the percentage of yield oftert-butyltrimethoxysilane was 91.1% by a gas chromatography internalstandard method, and the percentage of isolated yield by distillationunder reduced pressure was 70.0%.

[0159] The results of analysis of the isolatedtert-butyltrimethoxysilane by ¹H-NMR, ¹³C-NMR and GC-MS were as follows,and it was shown that the aimed product had a high purity.

[0160] H-NMR (CDCl₃): 1.043 ppm (s, 9H), 3.683 ppm (s, 9H)

[0161]¹³C-NMR (CDCl₃): 17.876 ppm, 26.410 ppm, 51.277 ppm

[0162] GC-MS: Mw=178, C₇H₁₈O₃Si

[0163] Further, the water content and the lithium content in theobtained tert-butyltrimethoxysilane were measured by means of a KarlFischer moisture meter and ICP-MS and as a result, H₂O=14 ppm and Li<10ppb, and the obtained product was useful as an insulating film material.

EXAMPLE 7

[0164] The same operation as in Example 3 was carried out except thatthe aimed product 1-adamantyltriethoxysilane was purified by isolationby means of distillation under reduced pressure instead of columnchromatography, to obtain the aimed product 1-adamantyltriethoxysilane.The percentage of yield was 74.0%.

[0165] The results of analysis of the isolated1-adamantyltriethoxysilane by ¹H-NMR, ¹³C-NMR and GC-MS were as follows,and it was shown that the aimed product had a high purity.

[0166]¹H-NMR (CDCl₃): 1.290 ppm (t, 9H), 1.836 ppm and 1.886 ppm (twopeaks, 15H), 3.890 ppm (q, 6H)

[0167]¹³C-NMR (CDCl₃): 18.499 ppm, 22.656 ppm, 27.453 ppm, 36.975 ppm,37.616 ppm, 58.785 ppm

[0168] GC-MS: Mw=298, C₁₆H₃₀O₃Si

[0169] Further, the water content and the lithium content in theobtained 1-adamantyltriethoxysilane were measured by means of a KarlFischer moisture meter and ICP-MS and as a result, H₂O=10 ppm and Li<10ppb, and the obtained product was useful as an insulating film material.

EXAMPLE 8

[0170] Film Formation by Plasma Polymerization ofTert-Butyltrimethoxysilane

[0171] For preparation of a thin film, an inductively coupled remoteplasma enhanced CVD apparatus (PECVD apparatus) as shown in FIG. 1 wasused. This apparatus mainly comprises a plasma source 1 made of quartzglass, a film formation chamber 2, a carburetor 3, a vacuum exhaustapparatus 4, a silicon substrate 5, a high frequency power source 6 anda matching network 7, and the film formation chamber 2 is equipped witha high sensitive infrared reflection absorption spectroscope (IRRAS) asshown in FIG. 2. The IRRAS is an apparatus to confirm the film formationstate of a polymer film in such a manner that infrared light 8 ispolarized by a polarizing plate 9 and irradiated on a polymer film to bedeposited on the silicon substrate 5 at an angle of incidence of 80°,and the reflected light from the polymer film is detected by amercury/cadmium/tellurium semiconductor infrared sensor 10. By usingthis apparatus, film formation by plasma polymerization of thetert-butyltrimethoxysilane prepared in Example 6 was carried out asfollows.

[0172] The film formation chamber 2 was evacuated of air to at most 10⁻⁴Pa, and then 5 sccm of oxygen gas was introduced, and the exhaustvelocity was adjusted by an orifice valve so that the pressure in thechamber would be 10 Pa. Then, the oxygen gas was eliminated, and atert-butyltrimethoxysilane gas as the material was introduced to thefilm formation chamber 2 through the carburetor 3 until the internalpressure would be 10 Pa. After the internal pressure was stabilized, ahigh frequency of 75 W was applied to the plasma source 1 to generateplasma, and a thin film was deposited on the silicon substrate 5installed in the film formation chamber 2. During this time, the flowrate of the tert-butyltrimethoxysilane gas was kept at 5 sccm, and filmformation was carried out for 12 minutes.

[0173] By measurement by the IRRAS at the time of film formation, it wasconfirmed that a polymer of silicon oxide having such a structure that atertiary butyl group was directly bonded to a silicon atom wasdeposited.

[0174] The obtained thin film by plasma polymerization on the siliconsubstrate was analyzed by means of an electron microscope (SEM), a X-rayphotoelectron spectroscope (XPS) and an infrared absorption spectroscope(IR), and the results are shown below.

[0175] Film thickness (SEM): 120 nm

[0176] Film formation (XPS): C=37 atom %, O=49 atom % and Si=14 atom %

[0177] C/Si=2.64

[0178] Infrared ray absorption (IR): Tertiary butyl group directlybonded to a silicon atom (2,956 cm⁻¹, 1,479 cm⁻¹, 727 cm⁻¹), methylgroup directly bonded to a silicon atom (2,853 cm⁻¹, 1,273 cm⁻¹, 798cm⁻¹)

COMPARATIVE EXAMPLE 4

[0179] Film Formation by Plasma Polymerization of MethylTrimethoxysilane

[0180] A thin film by plasma polymerization was formed on a siliconsubstrate in the same manner as in Example 8 except thatmethyltrimethoxysilane was used instead of tert-butyltrimethoxysilane,and the film formation time by polymerization was 20 minutes. Theresults of analysis are shown below.

[0181] IRRAS: Deposition of the polymer of silicon oxide having such astructure that a methyl group was directly bonded to a silicon atom wasconfirmed.

[0182] Film thickness (SEM): 22 nm

[0183] Film composition (XPS): C=37 atom %, O=43 atom % and Si=20 atom %C/Si=1.85

[0184] Infrared absorption (IR): Methyl group directly bonded to asilicon atom (2,853 cm⁻¹, 1,273 cm⁻¹, 798 cm⁻¹), hydrogen directlybonded to a silicon atom (broad peak in the vicinity of 2,300 cm⁻¹) andhydroxyl group directly bonded to a silicon atom (broad peak in thevicinity of 3,300 cm⁻¹)

[0185] It was confirmed that the film formation rate was slow, theamount of carbon uptake was small, and a polymer thin film having ahydroxyl group and hydrogen directly bonded to silicon, which wasinappropriate as an insulating film, was obtained, as compared withExample 8.

[0186] As mentioned above, it was found that by plasma polymerization oftert-butyltrimethoxysilane alone, a silicon oxide polymer thin filmhaving both tertiary butyl group and methyl group directly bonded to asilicon atom, having a high carbon content, useful as an insulatingfilm, can be obtained at a high film formation rate as compared with aconventional method.

EXAMPLE 9

[0187] Preparation of Tert-Butyldimethylchlorosilane

[0188] 258.2 g (2.00 mol) of dimethyldichlorosilane and 600 ml ofn-pentane were charged in a 3 L four-necked flask reactor equipped witha reflux condenser, a dropping funnel and a stirring apparatus, in anatmosphere of nitrogen, and cooled to 0° C. 539.6 g (2.00 mol) of an-pentane solution of 23.7 wt % tert-butyllithium was dropwise addedthereto from the dropping funnel over a period of 1 hour, and stirringwas carried out for 2 hours.

[0189] After the reaction, by-product lithium chloride was removed byfiltration, and n-pentane was distilled off from the filtrate, and thentert-butyldimethylchlorosilane as a purified product was isolated bydistillation. The yield was 235.1 g, and the percentage of isolatedyield was 78.0%.

[0190] Preparation of Tert-Butyldimethylethoxysilane

[0191] 156.9 g (1.04 mol) of tert-butyldimethylchlorosilane, 82.3 g(1.16 mol) of sodium ethoxide having a purity of 96% and 1.6 L ofn-hexane were charged in a 2 L separable flask reactor equipped with astirring apparatus in a stream of nitrogen, and reaction was carried outfor 22 hours under reflux of n-hexane.

[0192] The solid residue was collected by filtration by means of a glassfilter to obtain a reaction mixture solution. Analysis was carried outby means of gas chromatography, whereupon the percentage of yield of theaimed product tert-butyldimethylethoxysilane was 66.8%, and thepercentage of yield of by-product tert-butyldimethylhydroxysilane was33.2%.

[0193] Removal of By-Product and Purification ofTert-Butyldimethylethoxysilane

[0194] The above obtained reaction mixture was charged in a 2 Lseparable flask reactor equipped with a stirring apparatus in a streamof nitrogen, and 16.6 g (0.691 mol) of sodium hydride was added thereto,followed by stirring at room temperature for 1 hour. Analysis by gaschromatography was carried out, whereupon the amount of by-producttert-butyldimethylhydroxysilane was at most detection limit.

[0195] After completion of the reaction, the solid residue was collectedby filtration by means of a glass filter to obtain a reaction mixturesolution. n-Hexane was distilled off from the reaction mixture solution,and the aimed product tert-butyldimethylethoxysilane was isolated bydistillation at normal pressure.

[0196] The yield was 91.5 g (0.572 mol), corresponding to a percentageof yield of 55.0%.

[0197] The results of analysis of the isolatedtert-butyldimethylethoxysilane by means of ¹H-NMR, ¹³C-NMR and GC-MSwere as follows.

[0198]¹H-NMR: 0.079 ppm (s, 6H), 1.01 ppm (s, 9H), 1.13 ppm (t, 3H),3.56 ppm (q, 2H)

[0199]¹³C-NMR: 18.23 ppm, 18.66 ppm, 25.92 ppm, 58.51 ppm

[0200] GC-MS: Mw=160, C₈H₂₀OSi

[0201] Further, the water content and the sodium and lithium contents in100 g of the obtained tert-butyldimethylethoxysilane were measured bymeans of a Karl Fischer moisture meter and ICP-MS (inductively coupledplasma mass spectrometer, manufactured by Yokogawa Analytical System,Inc., tradename “HP-4500”) and as a result, H₂O=10 ppm, Na<10 ppb andLi<10 ppb, and the obtained product was useful as an insulating filmmaterial.

COMPARATIVE EXAMPLE 5

[0202] The same operation as in Example 1 was carried out except thatafter the reaction of tert-butyldimethylchlorosilane with sodiumethoxide of Example 9, sodium chloride and unreacted sodium ethoxidewere not removed by filtration, but water was added to carry out removalof the solution by separation and extraction, and further, by-producttert-butyldimethylhydroxysilane was not removed by the reaction withsodium hydride, to prepare tert-butyldimethylethoxysilane.

[0203] The water content and the sodium content in the obtainedtert-butyldimethylethoxysilane were measured by means of a Karl Fischermoisture meter and ICP-MS, whereupon H₂O=210 ppm and Na=98 ppm, and theobtained product was inappropriate as an insulating film material.

EXAMPLE 10

[0204] Preparation of Organic Lithium Having a Secondary Carbon Atom anda Lithium Atom Directly Bonded to Each Other

[0205] 15.8 g (239 mmol) of cyclopentadiene obtained by crackingdistillation of dicyclopentadiene and 50 ml of dry tetrahydrofuran werecharged in a 200 ml Schlenk tube reactor equipped with a dropping funneland a stirring apparatus in a stream of nitrogen, and cooled to −20° C.90.0 ml (239 mmol) of 2.66 mol/L n-butyllithium was dropwise addedthereto with stirring over a period of 45 minutes, and reaction wascarried out at −20° C. for 30 minutes and at room temperature for 1hour. After the reaction, the reaction liquid was added to 200 ml ofn-hexane, and the product cyclopentadienyl lithium was precipitated,collected by filtration by means of a glass filter and dried.

[0206] Preparation of Organic Silane Compound Having Such a StructureThat a Secondary Carbon Atom is Directly Bonded to a Silicon Atom

[0207] 50 ml of dry n-pentane, 20 ml of dry ether and 8.09 g (47.6 mmol)of tetrachlorosilane were charged in a 200 ml Schlenk tube reactorequipped with a stirring apparatus in a stream of nitrogen, and a liquidhaving 7.20 g (100 mmol) of the above prepared cyclopentadienyl lithiumslurried with 70 ml of n-pentane was dropwise added thereto by means ofan injector at room temperature over a period of 10 minutes. Aftercompletion of the dropwise addition, stirring was carried out at roomtemperature for 24 hours. After completion of the reaction, lithiumchloride was removed from the reaction liquid slurry by means of a glassfilter, and n-pentane was distilled off to obtaindicyclopentadienyldichlorosilane.

[0208] The obtained dicyclopentadienyldichlorosilane and 120 ml ofn-hexane were charged in a 200 ml Schlenk tube reactor equipped with areflux condenser and a stirring apparatus in a stream of nitrogen anddissolved. 8.17 g (120 mmol) of sodium ethoxide was added thereto, andreaction was carried out under reflux of n-hexane for 4 hours. After thereaction, sodium chloride and unreacted sodium ethoxide were removed byfiltration by means of a glass filter, and 7.41 g (29.9 mmol) of theproduct dicyclopentadienyldiethoxysilane was obtained by purification bydistillation. The percentage of yield was 62.8%.

[0209] The results of analysis of the isolateddicyclopentadienyldiethoxysilane by ¹H-NMR and GC-MS were as follows.

[0210]¹H-NMR: 6.25 ppm (m, 10H), 1.28 ppm (t, 6H), 3.91 ppm (q, 4H)

[0211] GC-MS: Mw=248, C₁₄H₂₀O₂Si

[0212] Further, the water content and the sodium and lithium contents in100 g of the obtained dicyclopentadienyldiethoxysilane were measured bymeans of a Karl Fischer moisture meter and ICP-MS (inductively coupledplasma mass spectrometer, manufactured by Yokogawa Analytical Systems,Inc., tradename “HP4500”) and as a result, H₂O=17 ppm, Li<10 ppb andNa<10 ppb, and the obtained product was useful as an insulating filmmaterial.

COMPARATIVE EXAMPLE 6

[0213] The same operation as in Example 1 was carried out except thatafter the reaction of dicyclopentadienyldichlorosilane with sodiumethoxide in “Preparation of organic silane compound having such astructure that a secondary carbon atom is directly bonded to a siliconatom” in Example 10, sodium chloride and unreacted sodium ethoxide werenot removed by filtration, but water was added to carry out removal ofthe solution by separation and extraction to preparedicyclopentadienyldiethoxysilane.

[0214] The water content and the sodium and lithium contents in theobtained dicyclopentadienyldiethoxysilane were measured by means of aKarl Fischer moisture meter and ICP-MS and as a result, H₂O=130 ppm,Li<10 ppb and Na<10 ppb, and the obtained product was inappropriate asan insulating film material.

[0215] According to the present invention, the following remarkableeffects are obtained.

[0216] The present invention provides a material having a low dielectricconstant and a high mechanical strength, as a low-dielectric constantmaterial for an interlayer insulating film of a semiconductor device, byusing the organic silane compound having such a structure that at leastone secondary hydrocarbon group and/or tertiary hydrocarbon group isdirectly bonded to a silicon atom of the present invention.

[0217] The present invention further provides a porous material whichcan hardly be obtained by a Conventional method, by applying the organicsilane compound having such a structure that at least one secondaryhydrocarbon group and/or tertiary hydrocarbon group is directly bondedto a silicon atom to formation of an interlayer insulating film byPECVD.

[0218] The entire disclosures of Japanese Patent Application No.2002-023988 filed on Jan. 31, 2002, Japanese Patent Application No.2002-112130 filed on Apr. 15, 2002, Japanese Patent Application No.2002-332100 filed on Nov. 15, 2002, Japanese Patent Application No.2002-346225 filed on Nov. 28, 2002 and Japanese Patent Application No.2002-346226 filed on Nov. 28, 2002 including specifications, claims,drawings and summaries are incorporated herein by reference in theirentireties.

What is claimed is:
 1. An insulating film material formed by chemicalvapor deposition, which contains an organic silane compound having sucha structure that at least one secondary hydrocarbon group and/ortertiary hydrocarbon group is directly bonded to a silicon atom.
 2. Theinsulating film material according to claim 1, wherein the organicsilane compound having such a structure that a tertiary hydrocarbongroup is directly bonded to a silicon atom has the following formula(1):

wherein each of R¹, R² and R³ is a C₁₋₂₀ hydrocarbon group, providedthat R¹, R² and R³ may be bonded to each other to form a cyclicstructure, R⁴ is a C₁₋₁₀ hydrocarbon group or a hydrogen atom, and a isan integer of from 1 to
 3. 3. The insulating film material according toclaim 2, wherein the tertiary carbon group in the formula (1) istertiary butyl, tertiary amyl or 1-adamantyl.
 4. The insulating filmmaterial according to claim 1, wherein the organic silane compoundhaving such a structure that a tertiary hydrocarbon group is directlybonded to a silicon atom has the following formula (2):

wherein each of R⁵ and R⁶ is a C₁₋₂₀ hydrocarbon group, each of R⁷ andR⁸ is a hydrogen atom or a C₁₋₂₀ hydrocarbon group, provided that aplurality of R⁵ 's, or R⁶ and R⁸ may be bonded to each other to form acyclic structure, and each of b and c is 0 or
 1. 5. The insulating filmmaterial according to claim 4, wherein the organic silane compound ofthe formula (2) is tert-butyldialkylalkoxysilane.
 6. The insulating filmmaterial according to claim 1, wherein the organic silane compoundhaving such a structure that a secondary hydrocarbon group is directlybonded to a silicon atom has the following formula (3):

wherein each of R⁹, R¹⁰ and R¹¹ is a C₁₋₂₀ hydrocarbon group, providedthat R⁹ and R¹⁰ may be bonded to each other to form a cyclic structure,R¹² is a C₁₋₁₀ hydrocarbon group or a hydrogen atom, d is an integer offrom 1 to 3, e is an integer of from 0 to 2, and d+e is an integer of atmost
 3. 7. The insulating film material according to claim 6, whereinthe secondary hydrocarbon group in the formula (3) is cyclopentadienyl.8. The insulating film material according to claim 1, wherein the amountof impurities derived from production materials, other than the elementsof silicon, carbon, oxygen and hydrogen, is less than 10 ppb, and thewater content is less than 50 ppm.
 9. The insulating film materialaccording to claim 1, wherein the chemical vapor deposition is plasmaenhanced chemical vapor deposition (PECVD).
 10. A method for producingan organic silane compound of the formula (1)

wherein each of R¹ to R⁴ and a is as defined above, which comprisesreacting organic lithium having a tertiary carbon atom and a lithiumatom directly bonded to each other, produced by reacting an organichalide of the following formula (4):

wherein each of R¹ to R³ is as defined above, and X is a chlorine atom,a bromine atom or an iodine atom, with metal lithium particles, with ahalogenated alkoxysilane or a tetraalkoxysilane of the following formula(5): X′_(m)Si(OR⁴)_(4-m)  (5) wherein R⁴ is as defined above, X′ is afluorine atom, a chlorine atom, a bromine atom or an iodine atom, and mis an integer of from 0 to
 3. 11. A method for producing an organicsilane compound of the formula (3):

wherein each of R⁹, R¹⁰, R¹¹, R¹², d, e and d+e is as defined above,which comprises reacting a compound having a secondary carbon atom and alithium atom directly bonded to each other, produced by reacting anorganic compound of the following formula (6):

wherein each of R⁹ and R¹⁰ is as defined above, and Y is a hydrogenatom, a chlorine atom, a bromine atom or an iodine atom, with organiclithium or metal lithium particles, with a halogenated silane, ahalogenated alkoxysilane or a tetraalkoxysilane of the following formula(7): Y′_(p)SiR¹¹ _(q)(OR¹²)_(4−(p+q))  (7) wherein Y′ is a fluorineatom, a chlorine atom, a bromine atom or an iodine atom, each of R¹¹ andR¹² is as defined above, p is an integer of from 0 to 4, q is an integerof from 0 to 2, and p+q is an integer of at most 4, and in a case wherea halogen atom which is directly bonded to silicon remains, reacting analkali metal alkoxide of the following formula (8) therewith: R¹²OM  (8)wherein M is an alkali metal, and R¹² is as defined above, followed bypurification by filtration, distillation or column separation.
 12. Aninsulating film formed by using the organic silane compound as definedin claim 1, by a PECVD apparatus.
 13. An insulating film, which isobtained by subjecting the insulating film as defined in claim 12 to aheat treatment at a temperature at which the bond between the tertiarycarbon atom and the silicon atom is broken or higher, to make the filmbe porous.
 14. A semiconductor device, which employs the insulating filmas defined in claim 12.